Over 36 million American women have low bone mass (bone mineral density [BMD] T-scores -1 to -2.49) and are at very high risk for progression to osteoporosis (BMD T-scores -2.50 or lower) and fractures. Osteoporosis and fractures are major health problems in the U.S. with annual expenditures of $19 billion, and the problem is growing. Our goal is to provide nurses and the wider healthcare community best practice guidelines by contributing evidence as to whether a lifestyle intervention should be implemented for women with low bone mass prior to use of bisphosphonate (BP) medications. In this study, women with low bone mass in the first 5 years of menopause (a time of rapid and significant bone loss) will be randomized to 3 groups (n =103 per group): 1) optimal calcium + vitamin D (optimal CaD) alone (Control); 2) a BP plus optimal CaD (Risedronate); or 3) a three times weekly bone loading exercise program plus optimal CaD (Exercise). Adequate calcium and vitamin D are necessary for bone; however, they frequently are not enough to prevent progression of bone loss in post-menopausal women. Although BPs are indicated for women with osteoporosis, their use is controversial for women with early bone loss. One concern is that long-term use of BPs may increase risk for atypical hip and femur fractures. A bone loading exercise program promotes bone health by improving bone structure and bone formation at sites of mechanical stress as well as by preserving BMD. Comparing effectiveness of exercises with BPs is critical because this will determine whether standard practice should include a trial of exercises prior to BP prescriptions in this at risk population. If an effective exercise program could substitute for, or delay the use of BPs, not only would bone health improve throughout the lifespan, but women would benefit from the many other positive effects of exercise. Our central hypothesis is that after 12 months of participation, improvements in bone strength will be greater in subjects randomized to the Exercise group compared to subjects in either the Control or Risedronate groups. We believe that the best predictor of fracture is bone strength, and strength is determined by bone structure and turnover as well as BMD. Thus, outcomes will include changes in bone structure at the tibia and hip (pQCT and Hip Structural Analysis); BMD at the total hip, femoral neck, and spine; and serum markers of bone formation and resorption. Because adherence to exercises and risedronate may be difficult for subjects to accomplish, education, goal setting, graphic feedback, and targeted strategies for barrier reduction will be used to promote adherence. Dr. Nancy Waltman has over 15 years' experience and 14 publications on the impact of exercise on bone in post-menopausal women. With the addition of Dr. Bilek and other expert consultants and co-investigators, we believe we are well-qualified to conduct this study. Our proposal is consistent with the NINR strategic plan to support research for patient self-management, disease prevention, & application of new technology (Hip Structural Analysis and pQCT).